To ensure network security, authentication is an important measure that can guarantee the authenticity of communication participants, the integrity of information, and the reliability of a source, which also prevents attacks resulting from illegal activities—such as falsifying information, altering data, and delaying communications. In cryptography, private-key cryptosystems and public-key cryptosystem are generally used to ensure the security, integrity, and non-repudiation of identity information, and provide a defense against identity impersonation attacks in communications. Quantum cryptography is an overlapping area of quantum mechanics and cryptography, and provides security ensured by fundamental principles of quantum mechanics, and which is irrelevant to the computing power and storage capacity of an attacker. Also, quantum cryptography has been proven to possess unconditional security and detectability from eavesdroppers. However, traditional quantum key distribution protocols do not provide an effective authentication mechanism; thus, it may be subject to man-in-the-middle or distributed denial of service (DDoS) attacks during the distribution process.
With respect to the above problems, two solutions have been presented as possible solutions:
(I) M. Dusek et. al holds that it is not necessary to authenticate all classical information during the communication, rather, only the classical information that affects the judgment of quantum state error rate. Thus, M. Dusek proposed a quantum authentication protocol that combines the classical message authentication algorithm, of which the essence is to utilize a classical authentication algorithm to authenticate a classical message as little as possible.
(II) BB84 protocol with authentication. The main differences between this protocol and the original BB84 protocol mainly lie in that some bits in a randomly sent quantum bit string are set as specific authentication bits, the positions of which are determined by authentication keys. Authentication of the communication participants are realized by a basis of measurement represented by the authentication bits and a polarization state of a quantum of light. Quantum state information of the authentication bit cannot be transmitted randomly, but is determined by the authentication key shared by the two participants as per a specific rule. A receiver and a sender sets part of the shared quantum key acquired from every negotiation as the authentication key to realize a dynamic update of the authentication key.
The security of the QKD process can be enhanced to a certain degree by applying the authentication mechanisms provided by the two schemes, but each scheme still has certain defects:
(I) For the M. Dusek scheme, it is vulnerable to man-in-the-middle attack or DDoS attacks due to a limited quantity of authentication keys shared by the communication participants in advance. This scheme does not take full advantage of quantum cryptography, and still applies a classical authentication technology, which leads to the risk of cracking.
(II) Although the BB84 protocol with authentication transmits the shared authentication key information in the form of a quantum state to improve the key distribution security, part of the shared quantum key acquired from every negotiation is required to be applied as the authentication key, which results in a waste of quantum key resources, as this part of the quantum key cannot be used for transaction data encryption.